Allow helper to map private ref names into normal names

This allows a helper to say that, when it handles "import
refs/heads/topic", the script it outputs will actually write to
refs/svn/origin/branches/topic; therefore, transport-helper should
read it from the latter location after git-fast-import completes.

Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-remote-helpers.txt

@@ -46,7 +46,11 @@ Supported if the helper has the "fetch" capability.
 'import' <name>::
 	Produces a fast-import stream which imports the current value
 	of the named ref. It may additionally import other refs as
-	needed to construct the history efficiently.
+	needed to construct the history efficiently. The script writes
+	to a helper-specific private namespace. The value of the named
+	ref should be written to a location in this namespace derived
+	by applying the refspecs from the "refspec" capability to the
+	name of the ref.
 +
 Supported if the helper has the "import" capability.
 
@@ -67,6 +71,16 @@ CAPABILITIES
 'import'::
 	This helper supports the 'import' command.
 
+'refspec' 'spec'::
+	When using the import command, expect the source ref to have
+	been written to the destination ref. The earliest applicable
+	refspec takes precedence. For example
+	"refs/heads/*:refs/svn/origin/branches/*" means that, after an
+	"import refs/heads/name", the script has written to
+	refs/svn/origin/branches/name. If this capability is used at
+	all, it must cover all refs reported by the list command; if
+	it is not used, it is effectively "*:*"
+
 REF LIST ATTRIBUTES
 -------------------
 

remote.c

@@ -673,6 +673,16 @@ static struct refspec *parse_push_refspec(int nr_refspec, const char **refspec)
 	return parse_refspec_internal(nr_refspec, refspec, 0, 0);
 }
 
+void free_refspec(int nr_refspec, struct refspec *refspec)
+{
+	int i;
+	for (i = 0; i < nr_refspec; i++) {
+		free(refspec[i].src);
+		free(refspec[i].dst);
+	}
+	free(refspec);
+}
+
 static int valid_remote_nick(const char *name)
 {
 	if (!name[0] || is_dot_or_dotdot(name))
@@ -811,6 +821,23 @@ static int match_name_with_pattern(const char *key, const char *name,
 	return ret;
 }
 
+char *apply_refspecs(struct refspec *refspecs, int nr_refspec,
+		     const char *name)
+{
+	int i;
+	char *ret = NULL;
+	for (i = 0; i < nr_refspec; i++) {
+		struct refspec *refspec = refspecs + i;
+		if (refspec->pattern) {
+			if (match_name_with_pattern(refspec->src, name,
+						    refspec->dst, &ret))
+				return ret;
+		} else if (!strcmp(refspec->src, name))
+			return strdup(refspec->dst);
+	}
+	return NULL;
+}
+
 int remote_find_tracking(struct remote *remote, struct refspec *refspec)
 {
 	int find_src = refspec->src == NULL;

remote.h

@@ -91,6 +91,11 @@ void ref_remove_duplicates(struct ref *ref_map);
 int valid_fetch_refspec(const char *refspec);
 struct refspec *parse_fetch_refspec(int nr_refspec, const char **refspec);
 
+void free_refspec(int nr_refspec, struct refspec *refspec);
+
+char *apply_refspecs(struct refspec *refspecs, int nr_refspec,
+		     const char *name);
+
 int match_refs(struct ref *src, struct ref **dst,
 	       int nr_refspec, const char **refspec, int all);
 

transport-helper.c

@@ -5,6 +5,7 @@
 #include "commit.h"
 #include "diff.h"
 #include "revision.h"
+#include "remote.h"
 
 struct helper_data
 {
@@ -12,6 +13,9 @@ struct helper_data
 	struct child_process *helper;
 	unsigned fetch : 1;
 	unsigned import : 1;
+	/* These go from remote name (as in "list") to private name */
+	struct refspec *refspecs;
+	int refspec_nr;
 };
 
 static struct child_process *get_helper(struct transport *transport)
@@ -20,6 +24,9 @@ static struct child_process *get_helper(struct transport *transport)
 	struct strbuf buf = STRBUF_INIT;
 	struct child_process *helper;
 	FILE *file;
+	const char **refspecs = NULL;
+	int refspec_nr = 0;
+	int refspec_alloc = 0;
 
 	if (data->helper)
 		return data->helper;
@@ -51,6 +58,21 @@ static struct child_process *get_helper(struct transport *transport)
 			data->fetch = 1;
 		if (!strcmp(buf.buf, "import"))
 			data->import = 1;
+		if (!data->refspecs && !prefixcmp(buf.buf, "refspec ")) {
+			ALLOC_GROW(refspecs,
+				   refspec_nr + 1,
+				   refspec_alloc);
+			refspecs[refspec_nr++] = strdup(buf.buf + strlen("refspec "));
+		}
+	}
+	if (refspecs) {
+		int i;
+		data->refspec_nr = refspec_nr;
+		data->refspecs = parse_fetch_refspec(refspec_nr, refspecs);
+		for (i = 0; i < refspec_nr; i++) {
+			free((char *)refspecs[i]);
+		}
+		free(refspecs);
 	}
 	return data->helper;
 }
@@ -72,6 +94,9 @@ static int disconnect_helper(struct transport *transport)
 
 static int release_helper(struct transport *transport)
 {
+	struct helper_data *data = transport->data;
+	free_refspec(data->refspec_nr, data->refspecs);
+	data->refspecs = NULL;
 	disconnect_helper(transport);
 	free(transport->data);
 	return 0;
@@ -119,6 +144,7 @@ static int fetch_with_import(struct transport *transport,
 {
 	struct child_process fastimport;
 	struct child_process *helper = get_helper(transport);
+	struct helper_data *data = transport->data;
 	int i;
 	struct ref *posn;
 	struct strbuf buf = STRBUF_INIT;
@@ -139,10 +165,16 @@ static int fetch_with_import(struct transport *transport,
 	finish_command(&fastimport);
 
 	for (i = 0; i < nr_heads; i++) {
+		char *private;
 		posn = to_fetch[i];
 		if (posn->status & REF_STATUS_UPTODATE)
 			continue;
-		read_ref(posn->name, posn->old_sha1);
+		if (data->refspecs)
+			private = apply_refspecs(data->refspecs, data->refspec_nr, posn->name);
+		else
+			private = strdup(posn->name);
+		read_ref(private, posn->old_sha1);
+		free(private);
 	}
 	return 0;
 }